President Bashar al-Assad's forces on Saturday destroyed the Omari mosque in the southern city of Daraa where Syria's uprising erupted two years ago, opposition activists said on Sunday, according to reports from AFP news agency.
In an amateur video uploaded to YouTube, the mosque's towering minaret can be seen toppling into a cloud of dust after an apparent shelling.
On Sunday, the opposition Syrian National Council reportedly blamed the regime for the attack.
According to AFP, the Council said: "This regime of unrestrained barbarism targeted with tanks the minaret of the Omari mosque, a place full of symbols of civilisation and spirituality and humanity."
"The minaret of this mosque, which was build by Caliph Omar bin al-Khattab, is the first in the whole of the Levant, and has been destroyed by the soldiers of the tyrant," it added, referring to President Assad.
The Omari mosque played a pivotal role in the beginning of the Syrian uprising as the first place demonstrators gathered in March 2011 to protest the arrest and alleged torture of teenagers who sprayed anti-Assad graffiti, sparking the waves of weekly peaceful demonstrations that eventually spread across the country.
At the start of the uprising, the mosque was briefly used as a civilian hospital for wounded protestors and, for the past two years, it has been a gathering place for anti-regime protestors.
"It was the first place that embraced the Syrian revolution during its infancy, the first wave of demonstrations of pride and dignity came out through its doors," said the Council.
Opposition group, the Local Coordination Committees of Syria (LCC), reportedly condemned the destruction of the minaret as a "barbaric act," adding: "It is not just stones that are destroyed but also religious and historic heritage cherished by the Syrian people."
According to CNN, the LCC said there was shelling using surface-to-surface missiles and phosphorus bombs in Daraa and other parts of the country on Saturday.
Opposition activists have reportedly told the news site that the government is using an increasing number of phosphorus bombs - incendiary weapons that can cause serious chemical burns - in its attacks.
According to the LCC, by the end of Saturday, 115 people were killed in Syria, including 12 in Daraa.
